Problems with APPENDs and INCLUDEs in BAPI Data Structures 
Problems with APPENDs and INCLUDEs in BAPI Data Structures
You must not use INCLUDE structures in BAPI structures, because enhancements to INCLUDE structures generally lead to incompatible changes to the BAPI structure. For more information about this, see
Incompatible Further Developments. 
Structure S1 consists of fields F1 and F2. Structure S2 includes structure S1 and has a field F3. If a field F3 is added to structure S1, this causes an incompatible change to structure S2 and leads to a name clash of the F3 fields.
The graphic below illustrates the problem:
